<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <!--<p id="pid">hello</p>-->
    <script >
//        document.getElementById("pid").innerHTML="miao9";
    </script>
    <script>
        var string = "hello";//字符串
        var i1=10;//数字
        var flag = true;//布尔类型
        var arr1 = new Array();//数组
        arr[0]=10;
        arr[1]=20;
        arr[3]=30;
//        document.write(arr[2]);//数组中arr[2]未定义会输出“undefined”
        var arr2 = [1,2,3,4];
        var arr3 = ["hello","miao","hi"];
        var n = null;
        i1 = null;
        document.write(n);
    </script>


</body>
</html>